Rail flaw detector mechanism



April 24, 1951 w, MESH 2,549,916

RAIL FLAW DETECTOR MECHANISM Filed July 28, 1948 2 Sheets-Sheet 1AMPLIFIER T 1 l L. I INVENTOR.

WILLIAM E. MESH ATTORNEY.

April 24, 1951 w, E MESH 2,549,916

RAIL FLAW DETECTOR MECHANISM Filed July 28, 1948 2 Sheets-Sheet 2 3 a.L. 8 FIG.3A

m 3 E OPERATING g O l 234.56789IOIII2I3 SPEED OF CAR (MILES PER HOUR) 2m 28 m A e 2 o 33 g I 3 E a I I 2 m I OPERATING I T g a f 1 v I RANGEI JE -E30 I 23456789IOII|2|3 LL 3 g SPEED OF CAR (MILES PER HOUR) 2: 65 mUNITY FIG.3C

OPERATING 1 AMPLIFIER OUTPUT IN VEN TOR. WILLIAM E. MESH AT TORNE Y.

RATE OF INCREASE 28 32 36 4O 44 48 OF SIGNAL VOLTAGE Patented Apr. 24,1951 RAIL FLAW DETECTOR MECHANISM William E. Mesh, Tcaneck, N. J.,assignor to Sperry Products, Inc., Hoboken, N. 3., a corporation of NewYork Application July 28, 1948, Serial No. 41,013

Claims.

This invention relates to rail flaw detector mechanisms and isparticularly designed for application upon the type of detectormechanism employed on the Sperry Rail Flaw Detector Car. This caroperates upon the principle of energizing the rail with flux, as, forinstance, by passing current through the rail to establish anelectromagnetic field surrounding the same, and exploring'said field byinductive means to discover any irregularities caused by the presence offissures or other discontinuities in the rail. The particular problemwhich presents itself arises from the fact that the speed of the car mayvary so that for the same discontinuity in the rail there may be induceda larger or smaller voltage depending upon the speed of the car. Sincethe voltage thus induced is designed, after amplification, to trip arelay when the output voltage of the amplifier exceeds a predeterminedvoltage, it will be seen that the tripping point may be reached by asmaller or larger discontinuity if the speed is increased or decreased,respectively.

It is, therefore, the principal object of this invention to provide amethod and means which will insure that the tripping output voltage ofthe amplifier will always represent the same size discontinuityregardless of the varying speed of the detector car.

Further objects and advantages of this invention will become apparent inthe following detailed description thereof.

In the accompanying drawings,

Fig. 1 is a side elevation of a portion of a rail fissure detector carhaving my invention applied thereto.

Fig. 2 is a wiring diagram of one embodiment of this invention.

Figs. 3A, 3B and 3C are a series of interrelated graphs illustrating theprinciple of this invention.

Fig. 4 is a view similar to a portion of Fig. 2 but showing a modifiedform of the invention.

Referring to Fig. 1 of the drawing, there are shown the parts of astandard Sperry rail fissure detector car which includes a car body l0operating along the rails R. Fissure detection is accomplished byenergizing the rail with flux, as, for instance, by passing currentthrough each rail from a generator G within the car body supplyingcurrent to spaced current brushes H and !2 supported upon the currentbrush carriage l3 which when in lowered or efiective position is adaptedto ride upon the rail by means such as wheels H5. The current brushcarriage is normally held in elevated or ineffective position by meansof springs, not shown, and cables !6, but When it is desired to lowersaid carriage, fluid pressure such as compressed air is supplied to thecylinders H to force out pistons 18 which are pivotally connected at [9to the current brush carriage [3. The current passed through the rail byway of spaced brushes II and I2 will establish an electromagnetic fieldsurrounding the rail and this field will be uniform except in the regionof flaw, Where it Will be distorted. Such distortions of theelectromagnetic field-are detected by a flaw responsive mechanismincluding housing 20 in which are positioned one or more pairs ofopposed induction coils 22.-The housing 28 is supported at a constantdistance above the rail surface by means of a carriage 24. Said carriage24 is mounted on current brush carriage 53 by means of loosely fittingbolts 25 and springs 26 to permit said carriage 2 2, while riding on therail on means such as wheels 21, to move independently of carriage 13 sothat the said carriage 24 may at all times maintain parallelism with therail surface regardless of irregularities thereof. The coils 22 normallycut the same number of lines of force, but on entering a region of fiaw,first one coil and then the other will cut a different number of linesof force to generate a differential E. which after being suitablyamplified by an amplifier A may be caused to actuate a pen P operatingon a chart C. At the same time that the pen is actuated, there isactuatedalso marking means which may take the form of a paint gunmounted on the current brush carriage I3 a sufficient distance behindthe fiaw responsive members 22 to compensate for the movement of the carand for the lag in operation of the paint gun. The rails are heldtogether by joints which may comprise an angle bar 32, bolts 33, andadditional members, all of which constitute the rail joint. This railjoint serves to deflect the current passing through the rails and varythe electromagnetic field surrounding the same. The irregularities ofthe angle bar will cause the detector coils to pick up a large number ofvariations not due to discontinuities in therail. Therefore, a pair ofjoint cut-out fingers and 60 pivoted at points 5| are provided beforeand after the detector unit, and designed to be tripped by the angle barto render ineffective the indicating mechanism for the interval that thedetector unit passes over the angle bar, as more fully disclosed inPatent No. 2,069,030 to H. C. Drake granted January 26, 1937.

The output from amplifier A will actuate the pen P against the action ofa spring 5! provided the output voltage through relay coil 5!] exceeds apredetermined magnitude. As explained in the introduction hereto. agiven discontinuity will cause coils 22, for example, to induce an E. M.F. which, after being amplified by amplifier A, yield an output voltagewhich exceeds the predetermined magnitude necessary to actuatenpen P.

3 However, if the speed of the car is reduced, it will be seen that thesame discontinuity will yield an output from the amplifier Which isbelow the predetermined operating magnitude. Conversely, a discontinuitywhich at one speed of the detector car induces a voltage which, afteramplification, is insufiicient to actuate the pen P will, if the speedof the car is increased sufiiciently, yield an output voltage which willactuate the pen. Since unavoidably the speed of the car varies withdilferent operating conditions such as difierent rail conditions, andsince it is desired that the tripping point or minimum voltage output ofthe amplifier which will cause actuation of pen P shall always representthe same size discontinuity, means must be provided for compensatin forthe variations introduced by the varia tions in speed of the car. Thus,for example, if it is desired to indicate all fissures in excess of 10%area of the head regardless of the speed of the car, then it is seenthat means must be pro vided for preventing a 5% fissure from actuatingthe pen when the speed of the car is doubled. Similarly, means must beprovided for preventing the failure of the pen P to operate at a 15%fissure because the speed of the car has been reduced to half.

The basis of the solution offered by the present invention to the aboveproblem is disclosed in the graphs of Figs. 3A, 3B and 3C. will be seenthat in the operating range of the car between 7 and 12 miles per hourthe searching unit output voltage which resembles a sine curve will riseapproximately 32%. At the same time the rate of increase of the outputvoltage is in direct ratio, i. e., /vths or 71.5%, as shown in graph 33.It is this latter fact which is utilized to provide the solution of theproblem which constitutes this invention.

I provide an amplifier A of a type whose voltage output decreases withincrease in the rate of the signal voltage input. Such an amplifier is alow-pass frequency amplifier with gradual cut-01f so that the outputvoltage falls ofi Wit increase in the rate of the input signal voltage.Specifically, such an amplifier employs a filter unit-55 comprisingcapacitor 55 and resistor 51 in parallel. The constants of the filter55, i. e., the specific values of the capacitor 55 and resistor 57 areso chosen as to give the desired ratio. In this case, it is desired thatthe output voltage from the amplifier decrease about 32% as the inputrate of voltage change varies over the operating range disclosed in Fig.3B. Thus, while in the operating range of car speed from 7 to 12 milesper hour, the induced signal voltage increases 32% and the rate of theinduced signal voltage increases from a rate corresponding to 28 to arate corresponding to 48, the output voltage of the amplifier inresponse to such increased rate of signal voltage input should decrease32%. If graphs 3A and 3C are compared, it will be seen that the graph 3Ais at every point in the operating range the same percentage above unityas the amplifier output voltage is below unity. Thus, at every point inthe operating range the output voltage of the amplifier compensates forthe increased speed to the extent necessary to give a uniform constantoutput of the amplifier for any given discontinuity in the railregardless of variation of speed within the operating range.

In a modified form of the invention, a linear amplifier A may beemployed, and the low-pass filter 55 with gradual cut-off may bepositioned in advance of the amplifier, as shown in Fig. 4.

In graph 3A Having described my invention, what I claim and desire tosecure by Letters Patent is:

1. In a rail flaw detector car, means for energizing the rail with flux,detector means responsive to variations in said flux caused by a defectand adapted to induce a voltage Whose magnitude and rate of increase arefunctions of the speed of the car, and a low-pass filter connected tosaid detector means and having gradual cut-off for discriminating aidinduced voltages, whereby the output from said filter diminishes as therate of increase of the induced voltage increases.

2. In a rail flaw detector car, means for energizing the rail with fiux,detector means responsive to variations in said flux caused by a defectand adapted to induce a voltage Whose magnitude and rate of increase arefunctions of the speed of the car, and a low-pass amplifier connected tosaid detector means and having gradual cut-off for amplifying saidinduced voltages,

whereby the amplifier voltage output diminishes as the rate of increaseof the voltage input increases.

3. In a rail flaw detector car, means for ener gizing the rail withflux, detector means responsive to variations in said fiux caused by adefect and adapted to induce a voltage whose magnitude and rate ofincrease are functions of the speed of the car, and an amplifierconnected to said detector means for amplifying said induced voltages,said amplifier having means whereby the amplifier voltage output isconstant for any given defect regardless of the speed of the car, saidlast named means including a low-pass filter a with gradual cut-01f.

4. In a rail fiaw detector car, means for energizing the rail with flux,detector means responsive to variations in said fiux caused by a defectand adapted to induce a voltage whose magnitude and rate of increase arefunctions of the speed of the car, and an amplifier connected to saiddetector means for amplifying said induced voltages, said amplifierincluding a low-pass filter with gradual cut-off, the constants of saidfilter being of such values that the amplifier output with gradualcut-off, the constants of said filter being such values that for anygiven defect the amplifier output voltage diminishes as the rate ofincrease of the input voltage increases and to the same degree that theinduced voltage increases with increased speed.

WILLIAM E. MESH.

REFERENCES CITED The following references are of record in the file ofthis patent:

Ui-II'IED STATES PATENTS Number Name Date Re. 18,555 Sperry Aug. 2, 19322,264,873 Cockrell Dec. 2, 1941 2,265,135 Barnes et al Dec. 9, 19412,488,277 Falk et al Nov. 15, 1949

